On the impact of Cr and Ag additions on the grain boundary microchemistry, hydrogen permeability and environmentally assisted cracking mechanism of an Al-Zn-Mg-Cu-Zr 7xxx alloy
Chijioke Kenneth Akuata, Oliver Beyß, Lisa T. Belkacemi, Kerstin Hantzsche, Matthew E. Curd, Daniela Zander
Abstract
This study explored the impact of minor Cr and Ag additions on the resistance of a new generation Al-8Zn-2Mg-2Cu-0.1Zr alloy to hydrogen environmentally assisted cracking (HEAC) in humid air . The results show that HEAC in Al-8Zn-2Mg-2Cu-0.1Zr alloy can be suppressed by 0.1 wt% Cr addition, due to the formation of E-Al 18 Mg 3 Cr 2 dispersoids with a high H binding energy and possibly a less electrochemically active grain boundary (GB) microchemistry. ∼ 0.3 wt% Ag addition in Al-8Zn-2Mg-2Cu-0.1Zr alloy had no influence on the HEAC susceptibility , despite 1 at% Ag partitioning in the GB η -Mg(Zn,Cu,Al) 2 and a minor decrease in the PFZ width.